U.S. patent application number 15/901502 was filed with the patent office on 2018-08-23 for vascular implant.
The applicant listed for this patent is Silk Road Medical, Inc.. Invention is credited to Roy Leguidleguid, Herbert Mendoza, Michael P. Wallace.
Application Number | 20180235789 15/901502 |
Document ID | / |
Family ID | 63166691 |
Filed Date | 2018-08-23 |
United States Patent
Application |
20180235789 |
Kind Code |
A1 |
Wallace; Michael P. ; et
al. |
August 23, 2018 |
VASCULAR IMPLANT
Abstract
Methods and devices relate to the use and construction of a
vascular stent. A stent assembly includes mesh structure that is at
least partially attached to a support or stent structure. The stent
structure is formed of one or more struts that collectively form a
tubular body sized to fit within a blood vessel. The mesh structure
is formed of one or more filaments or sutures that are interwoven
or knit to form a structure that is coupled to the stent structure.
The mesh structure can at least partially cover or at least be
partially covered by the stent structure.
Inventors: |
Wallace; Michael P.;
(Sunnyvale, CA) ; Mendoza; Herbert; (Sunnyvale,
CA) ; Leguidleguid; Roy; (Sunnyvale, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Silk Road Medical, Inc. |
Sunnyvale |
CA |
US |
|
|
Family ID: |
63166691 |
Appl. No.: |
15/901502 |
Filed: |
February 21, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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62461616 |
Feb 21, 2017 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61F 2/07 20130101; A61F
2/915 20130101; A61F 2002/91566 20130101; A61F 2002/91575 20130101;
A61F 2/90 20130101; A61F 2002/9155 20130101; A61F 2/852 20130101;
A61F 2210/0076 20130101; A61F 2/86 20130101 |
International
Class: |
A61F 2/915 20060101
A61F002/915 |
Claims
1. A stent assembly adapted to be implanted in a blood vessel,
comprising: an inner stent structure formed of a plurality of
interconnected struts; an outer stent structure formed of a
plurality of interconnected struts, the inner stent structure
positioned within the outer stent structure to form a space
therebetween, wherein the inner stent structure and outer stent
structure collectively form a stent body sized and shaped to fit
within a blood vessel; a mesh structure positioned at least
partially in the space between the inner stent structure and outer
stent structure such that the mesh structure is attached to the
inner stent structure and outer stent structure in a sandwich
arrangement.
2. The stent assembly of claim 1, wherein the inner stent structure
exerts higher radial outward force than the outer stent structure
such that a net resulting force between the inner and outer stent
structures pushes the entire stent body toward a blood vessel wall
when implanted in a blood vessel.
3. The stent assembly of claim 1, wherein the struts of the inner
stent structure are shorter than the struts of the outer stent
structure.
4. The stent assembly of claim 1, wherein the mesh structure is
made of a shape memory alloy.
5. The stent assembly of claim 1, wherein the mesh structure forms
a plurality of tear drop shaped pores, and wherein at least two of
the tear drop shaped pores have enlarged rounded regions on a first
end and smaller regions on a second end, and wherein enlarged
rounded regions of at least two of the tear drop shaped pores are
in contact with one another.
6. The stent assembly of claim 1, wherein the mesh structure
includes a hem.
7. The stent assembly of claim 6, wherein the hem defines a space
in which at least one of the inner stent structure and outer stent
structure is at least partially positioned.
8. The stent assembly of claim 6, wherein the hem is integrally
attached to the hem structure.
9. The stent assembly of claim 6, wherein the hem is attached to
the hem structure by thread.
10. The stent assembly of claim 1, wherein at least a portion of
the mesh structure is formed of a polymer and a portion of the
stent structure is Nickel Titanium.
11. A method of forming a stent assembly comprising: forming an
inner stent structure of a plurality of interconnected struts;
forming an outer stent structure of a plurality of interconnected
struts; positioning the inner stent structure within the outer
stent structure to form a space therebetween, wherein the inner
stent structure and outer stent structure collectively form a stent
body sized and shaped to fit within a blood vessel; positioning a
mesh structure at least partially in the space between the inner
stent structure and outer stent structure; sandwiching the mesh
structure in the space between the inner stent structure and outer
stent structure to attached the mesh structure to the inner stent
structure and outer stent structure.
12. The method of claim 11, further comprising forming a hem on the
mesh structure.
13. The method of claim 12, further comprising positioning at least
a portion of one of the inner stent structure and outer stent
structure within the hem.
14. The method of claim 12, wherein forming a hem on the mesh
structure comprising attaching a hem to the mesh structure.
15. The method of claim 12, wherein forming a hem on the mesh
structure comprising folding a portion of the mesh structyure over
itself.
16. The method of claim 11, further comprising forming a plurality
of plurality of tear drop shaped pores in the mesh structure.
17. The method of claim 11, wherein the tear drop shaped pores are
arranged so that at least two of the tear drop shaped pores have
enlarged rounded regions on a first end and smaller regions on a
second end, and wherein enlarged rounded regions of at least two of
the tear drop shaped pores are in contact with one another.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority under 35 U.S.C.
.sctn. 119 to U.S. Provisional Application No. 62/461,616 filed
Feb. 21, 2017, the disclosure of which is incorporated herein by
reference. The provisional application is incorporated by reference
in its entirety.
BACKGROUND
[0002] Stents for transluminal implantation are generally made of
metallic supports that are inserted into a part of the human body
such as inside a blood vessel. Stents are usually generally
cylindrical and are constructed and arranged to expand radially
once in position within the body. Some stents include a graft or
mesh structure that can be used to minimize or eliminate the risk
of disease herniating through a body-implanted stent during a
healing phase.
[0003] The mesh structure of a stent assembly can add to the
overall width of the stent, which can be undesirable. It is
therefore desirable to manufacture a stent such that the mechanical
attachment between the mesh structure and stent structure is
efficient from a size standpoint. It also is important that the
mesh structure be properly and securely attached to the support
portion of the stent.
SUMMARY
[0004] Disclosed herein are methods and devices related to the use
and construction of a vascular stent assembly. A stent assembly
includes a mesh structure that is positioned over and/or at least
partially attached to a stent structure. Also disclosed are devices
and methods for securely attaching the mesh structure to the stent
structure. The stent assembly can also include or be coupled with a
stent delivery system that is configured to deliver the stent
assembly into a blood vessel of a patient.
[0005] In one aspect, there is disclosed a stent assembly adapted
to be implanted in a blood vessel, comprising: an inner stent
structure formed of a plurality of interconnected struts; an outer
stent structure formed of a plurality of interconnected struts, the
inner stent structure positioned within the outer stent structure
to form a space therebetween, wherein the inner stent structure and
outer stent structure collectively form a stent body sized and
shaped to fit within a blood vessel; and a mesh structure
positioned at least partially in the space between the inner stent
structure and outer stent structure such that the mesh structure is
attached to the inner stent structure and outer stent structure in
a sandwich arrangement.
[0006] In another aspect, there is disclosed a method of forming a
stent assembly comprising: forming an inner stent structure of a
plurality of interconnected struts; forming an outer stent
structure of a plurality of interconnected struts; positioning the
inner stent structure within the outer stent structure to form a
space therebetween, wherein the inner stent structure and outer
stent structure collectively form a stent body sized and shaped to
fit within a blood vessel; positioning a mesh structure at least
partially in the space between the inner stent structure and outer
stent structure; and sandwiching the mesh structure in the space
between the inner stent structure and outer stent structure to
attached the mesh structure to the inner stent structure and outer
stent structure.
[0007] Other features and advantages should be apparent from the
following description of various embodiments, which illustrate, by
way of example, the principles of the disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 shows an example stent assembly.
[0009] FIG. 2 shows a schematic representation of a hem structure
that is used to attach a mesh structure to a stent structure.
[0010] FIG. 3 shows an example wherein a meltable polymer leader is
attached to a Nickel Titanium (NiTi) mesh structure.
[0011] FIG. 4 shows a schematic representation of a stent assembly
that includes two stent structures including an inner stent
structure and an outer stent structure that form a space
therebetween in which the mesh structure can be positioned and
attached.
[0012] FIG. 5 shows an embodiment wherein a separate sandwiching
retainer element is attached to a stent structure.
[0013] FIG. 6 shows an example of a filament being hand sewn
through the end of a mesh structure.
[0014] FIG. 7 shows an enlarged view of a crown region of a stent
structure having a closed loop anchor and an open loop anchor.
[0015] FIG. 8 shows an embodiment of an anchor that can be located
on a crown of the stent structure.
[0016] FIG. 9 shows an example stent assembly with tear drop shaped
pores.
DETAILED DESCRIPTION
[0017] Disclosed herein are methods and devices related to the use
and construction of a vascular stent. A stent assembly includes
mesh structure that is positioned over and/or at least partially
attached to a support or stent structure. The stent structure is
formed of one or more struts that collectively form a tubular body
sized to fit within a blood vessel. The mesh structure is formed of
one or more filaments or sutures that are interwoven or knit to
form a structure that is coupled to the stent structure pursuant to
any of the configurations described herein. The mesh structure can
at least partially cover or at least be partially covered by the
stent structure.
[0018] The stent assembly can also include or be coupled with a
stent delivery system that is configured to deliver the stent
assembly into a blood vessel of a patient. An example stent
delivery system includes an elongated stent delivery catheter that
can be inserted into a blood vessel such as in a percutaneous
manner. The stent assembly can be mounted on the stent delivery
catheter such as on a distal region of the stent delivery catheter.
The stent delivery catheter can then be deployed to a target site
and the stent assembly can be released from the stent delivery
catheter so that the stent assembly deploys and is retained in
target location in the blood vessel.
[0019] The stent assembly can be used for implanting in any blood
vessel including the carotid artery. The mesh structure of the
stent assembly can be used to minimize or eliminate the risk of
disease herniating through the stent during a healing phase in
which the stent assembly is implanted in a patient, such as during
the first 30 days of implantation.
[0020] The stent assembly can be any stent, including a
self-expanding stent, or a stent that is radially expandable by
inflating a balloon or expanded by an expansion member. The stent
can also be made of any desired material, including a metallic
material, a metal alloy (e.g., nickel-titanium) or even polymeric
composites. The stent can have any wire or cell design. The vessels
in which the stent of the present invention can be deployed include
but are not limited to natural body vessels such a blood
vessel.
[0021] Various examples of mesh configurations for coupling to a
stent structure are described herein. The mesh configurations can
include, for example, (1) material of the mesh; (2) thread
configurations of the mesh; (3) size and quantity of filaments that
form the mesh; (4) modes of attachment between the mesh and the
stent, etc., and combinations thereof. Various embodiments of the
stent structure for attaching to the mesh structure are also
described herein.
[0022] FIG. 1 shows a perspective view of a stent assembly 100 that
includes a stent body 105 (or stent structure) that is coupled to a
mesh body 110 (or mesh structure). The stent body is a formed of a
plurality of interconnected struts or wires that are attached to
one another to form a plurality of cells or openings. The struts
can be attached to one another in any of a variety of manners. The
stent body generally forms a cylindrical shape that is sized and
shaped to fit within a blood vessel, such as a carotid artery.
[0023] In an embodiment, the mesh structure (sometimes referred to
as "knit") is made of a shape memory alloy, such as Nickel Titanium
(NiTi or Nitinol). In an example embodiment, the mesh structure
formed of a 0.0005 inch nitinol filament positioned over the stent.
In another example embodiment, the mesh structure is formed of a
polyester monofilament or multifilament.
[0024] A stent with a Polyethylene terephthalate ("PET") mesh
structure can be crimped down on to the stent structure for loading
onto a delivery system. The mesh structure has a wall thickness
such that it does not increase or significantly increase the
overall thickness of the entire stent assembly. In this regard, the
mesh structure may be dimensioned such that it has a wall thickness
that is less than double the wall thickness of the stent
structure.
[0025] There are now described various structures and methods for
attaching the mesh structure to the stent structure.
[0026] Attachment Via Glue
[0027] In an embodiment for attaching the mesh structure 110 to the
stent structure 105, a hem is formed and is used as a mechanical
interface between the mesh structure 110 and the stent structure
105. For example, a planar portion of the material that is used to
form the mesh structure is turned over itself to form such a hem.
The hem defines a space in which a corresponding portion of the
stent structure 105 can be inserted and secured. FIG. 2 shows a
schematic representation of the hem structure 205, which is
attached to the mesh structure 110 and to the stent structure
105.
[0028] The separate hem structure 205 is attached to the mesh
structure 110 such as via sewing or gluing. Then the mesh structure
110 is glued to the stent structure 105 via any of a variety of
methods. For example, the mesh structure can be soldered to the
stent structure such as by gold soldering a NiTi mesh structure to
the stent structure. Alternatively, a polymer glue, a melt, a
solvent polymer bond, etc. or a conformal polymer coating can be
used. FIG. 3 shows some examples of this wherein a meltable polymer
leader 305 is attached to an NiTi mesh structure 110. The attached
polymer portion of the mesh structure is then melted, bonded, or
otherwise mechanically attached to the stent structure.
[0029] In this manner, the stent assembly includes a transition
from a shape memory material, such as Nitinol, to a polymer
material at an end of the stent assembly.
[0030] Mechanical Attachment Via Sandwiching
[0031] In another embodiment for attaching the mesh structure 110
to the stent structure 105, the mesh structure 110 is sandwiched
between an inner stent structure 105a and an outer stent structure
105b. That is, the stent assembly includes two stent structures
including an inner stent structure 105a and an outer stent
structure 105b, as shown schematically in FIG. 4. The stent
structures 105a and 105b form a space therebetween in which the
mesh structure 110 can be at least partially positioned. In this
manner, the mesh structure 110 is interposed or sandwiched between
the stent structures 105a and 105b to form a secure attachment
therebetween.
[0032] In an example, the following specifications can be used for
the inner stent structure and outer stent structure: [0033] A
0.003'' outer stent structure over a NiTi mesh structure and a
0.006'' inner stent structure; [0034] A 0.002'' outer stent
structure over a NiTi mesh structure and a 0.008'' or 0.009'' inner
stent structure.
[0035] As shown in FIG. 5, in another sandwich embodiment, a
separate sandwiching retainer element 505 is added on crown ends of
the stent structure only. The mesh structure is not shown in FIG.
5.
[0036] The sandwich embodiments are now described further. An inner
stent structure and an outer stent structure can encapsulate a mesh
structure by placing the mesh structure therebetween. The inner
stent structure exerts higher radial strength or radially outward
force than the outer stent structure such that a net resulting
force between the inner and outer stent structures pushes the
entire stent assembly devices toward a blood vessel wall (e.g.,
radially outward) when implanted. Length-wise, both the inner stent
structure and outer stent structure are longer than the length of
the mesh structure. In an embodiment, both the inner stent
structure and outer stent structure have identical specifications
except two parameters. The first parameter is of strut length (SL)
for the struts of the stent structure. The second parameter is a
wall thickness (wt) of the stent structure.
[0037] In an example, the SL of the inner stent structure about 15%
shorter and the SL of outer stent structure is about 15% longer.
That is, all of the strut lengths of the inner stent structure are
smaller than the shortest strut of the outer stent structure. The
net difference in SL is 30% between inner stent structure and outer
stent structure. By having shorter SL, the radial strength becomes
higher. By having longer SL, the radial strength becomes lower.
Thus, the radial strength of the entire stent assembly device
exerts its radial strength outward (i.e., toward the blood vessel
wall).
[0038] The wt of the inner stent structure is 0.006'' and the wt of
outer stent structure is 0.003''. By having thinner wt, the radial
strength becomes lower. By having thicker wt, the radial strength
becomes higher. Thus, the radial strength of the composite device
exerts its radial strength outward (e.g., toward the vessel wall
direction). Also the net wt of the composite device is at or below
a 0.009'' threshold wt. By having both wt and SL tailored for
either higher or lower radial strength for both inner and outer
stents, respectively, the net radial strength of the composite
device exerts outward force toward the vessel wall.
[0039] Attachment Via Machine Sewing
[0040] As mentioned, a hem can be formed on the mesh structure. The
mesh can be formed using a sewing machine and the hem is attached
to the stent structure. The mesh structure can also be machine
sewed directly onto the struts of the stent structure. Pursuant to
such a process, a filament is used to form a stitch pattern that
attaches the mesh structure to the stent structure. The sewing
stich pattern can be formed from any variety of filaments
including, for example, 205 hand stitch and 301 lock stitch. The
stitching can be formed along struts of the stent (or just across
struts of the stent) in a circumferential orientation. The stitch
width can be constant or vary around the device's
circumference.
[0041] The stitch can have a constant or a variable stitch length.
For example, the stitch can be tighter at a certain number of
discrete locations along the stent structure and less tight at
remaining locations. The knit structure can also form pores of
various shapes and sizes.
[0042] Attachment Via Hand Sewing
[0043] In another embodiment, the mesh structure is attached to the
stent structure by hand sewing ends of the mesh structure to itself
and/or to the stent. Preferred sewing patterns can be used with
custom features on stent to make it easier to attach a suture onto
the stent. Example sewing patterns include test 301 lock stitch and
205 hand stitch.
[0044] FIG. 6 shows an example of a filament 605 being hand sewn
through the end of the mesh structure 110. Individual loops of
suture are then used to attach the mesh structure to the crowns of
the stent structure. The filament is sewed so that it runs in and
out of the loops. The quantity of loops may vary. In an embodiment,
there are 10 to 100 loops.
[0045] In an embodiment, a filament (such as a PET filament) is
sewn through the end of a NiTi mesh structure and connected to the
stent structure. The filament is sewn through one or more loops of
the mesh structure and also through donut holes or apertures along
the crown of the stent structure.
[0046] Attachment Via Hand Sewing with Suture Anchors
[0047] A crown region of the stent assembly can include one or more
types of suture anchors. The crown of the stent includes a first
type of suture anchor with a "split O" configuration in which the
suture anchor forms a partial loop with a gap or opening along its
circumference. The gap or opening provides a passage for the suture
to be inserted into the anchor.
[0048] The second type of suture anchor is a "solid circle" or
closed loop in which the suture anchor forms a completely closed
loop. FIG. 7 shows an enlarged view of the crown region of a stent
structure having a closed loop anchor 705 and an open loop anchor
710. The suture can be looped through the open loop anchor and
secured in a cleat manner, wherein the suture also extends through
the open loop anchor. The suture can alternately be looped around
the closed loop anchor and also be wrapped around a base of the
anchor to further secure the suture thereto.
[0049] The mesh structure is desirably secured to the stent
structure in a manner that will secure the mesh structure to the
stent structure against forces applied in both a distal direction
and a proximal direction along a longitudinal axis of the stent
structure. That is, the mesh structure will remain secured and not
detach from the stent structure regardless of a direction of
relative force between the stent structure and the mesh
structure.
[0050] FIG. 8 shows an embodiment of an anchor 805 that can be
located on a crown of the stent structure. The anchor forms a
closed loop and includes one or more "ears", prongs, barbs, or
protrusions 810 that serve as structure for further securing the
suture to the anchor. As shown in FIG. 8, the suture 805 can wrap
through the closed loop and also around the ears to secure the
suture thereto and prevent it from disengaging from the stent
structure during loading and/or removal of the stent assembly from
a delivery system. It should be appreciated that the ear structures
are just examples and that other structures can be used to further
secure the suture to the stent structure.
[0051] Mechanical Attachment Via Interconnecting Features
[0052] In another embodiment, the mesh mechanically interconnects
with features of the stent. Various methods can be used to
mechanically attach the mesh structure to the stent structure. For
example, the end of the mesh structure can be looped over the end
of the stent structure or the mesh structure is looped inside
itself with both layers of the knit on the outside of the stent.
The two knit layers can then be bonded or sutured together with
this construct.
[0053] Alternatively, the end of the knit can be "finished" so that
the filament used for the knitting does not unwind or unknit. The
end of the knit is secured with any of the methods described in
this disclosure. Next, the ends of the mesh structure are looped
over some features of the stent. These features may include the
crowns of the stent or finger-like protrusion structure. The
protrusions may be directed away or outwardly to help the mesh
structure to more easily engage.
[0054] Attachment Via Polymer Coating
[0055] In another embodiment, a polymer coating can be used to
finish the ends of the mesh structure and/or attach the mesh
structure to the stent structure. A thin layer of polymer is added
on the end of the mesh structure to prevent the mesh structure from
unraveling before attaching to the stent structure.
[0056] Alternately, a polymer coating is used to both help "finish"
the end of the mesh structure and also act as a mechanism to attach
mesh stent struts all at one time. For this example, the polymer
can be sprayed on just the ends of the stent assembly thereby
leaving the center of the stent/mesh structure clear of any
polymer. The polymer coating can be applied to one or more rows of
knit elements, less than one row of knit element, one or more strut
rung element, or less than one strut rung element. To coat just the
end of the knit, it may be required to mask the center of the stent
structure with a masking agent that can be removed after the
coating process is complete.
[0057] The polymer coating can be achieved with a dip or spray
process with various levels of solids. Multiple passes may be
required to get adequate coating. The key will be to encapsulate
the entire knit filament-stent strut element with the coating to
ensure it is adequately attached.
[0058] A variety of polymer gluing or coating options to secure
mesh end and/or bond to stent are shown in table below.
TABLE-US-00001 Stent Company Polymers Reference Cypher Cordis
Parylene C primer Cypher IFU Blend of: (2003) Cordis
Polyethylenevinyl acetate (PEVA); Polybutylmethacrylate (PBMA)
Taxus Boston Poly(styrene-isobutylene- Taxus Express2 Scientific
styrene) IFU (2012) SIBS Boston Scientific Endeavor Medtronic
Phosphorocholine (PC) EuroInterv (2007) 3: 137-139 Endeavor
Metronic Blend of: J Biomed Mater Res Resolute Polyvinylpyrrolidone
(2008) 85A: 1064- (PVP); Poly(butyl- 1071 methacrylate/vinyl
acetate) (C10); Poly(vinylacetate/ vinylpyrrolidone/
hexamethacrylate) (C19) Xience Guidant/ Copolymer of Cath
Cardiovasc Abbott Poly(vinyidene fluoride - Inter (2006) 68:
hexafloropropylene) 97-103 Other Misc PET, Pebax, Silicone,
Urethanes, parylene m and/or C with or without functional groups,
biomer
[0059] Other materials that can be used include, for example:
[0060] Parylene C: Conformal coating formed by vapor deposition.
Long history with medical devices.
[0061] PEVA: Rubbery copolymer. Available in broad range of vinyl
acetate ranges. Very low VA content (less than 10%) is difficult to
dissolve. Higher VA (18-33%) would be very flexible and
adhesive
[0062] PBMA: Hard, tough material. Not as flexible as PEVA. Easily
dissolvable in several solvents.
[0063] SIBS: Tough, rubbery material. Dissolvable in several
solvents.
[0064] PC: Tends to form as a self-assembled monolayer.
[0065] PVP: Water soluble polymer.
[0066] Polyvinylidenefluroide/hexafluoropropylene Melt
processible.
[0067] Attachment Via Welding
[0068] In another embodiment, the mesh structure can also be welded
to the stent structure. For example, the following materials can be
used in the weld process: [0069] Niti wire (from Knit) to Niti
stent weld: Laser welding, resistance welding [0070] Polymer
filament (from Knit) to Niti stent weld
[0071] Various mesh constructions can be used. A circular knitting
method can be used wherein the pore size can be formed from any one
of more polymer or metallic fiber or combinations there of. Example
NiTi or PET fibers are about 0.001'', 0.00075'', 0.0005'' diameter
wires.
Exemplary Cell Pattern for Mesh or Stent Structure
[0072] In an embodiment shown in FIG. 9, the knit or mesh structure
can be formed and/or post proccessed to form a kissing pore or cell
pattern. For example, the mesh structure forms a plurality of tear
drop shaped pores 905 with enlarged rounded regions on a first end
and smaller, pointed regions on a second end. In the kissing
pattern, the enlarged rounded regions of at least two of the tear
drop shaped pores are in contact or abut with one another. A tear
drop shaped pore can extend along a long axis with the rounded
region of a pore being positioned along the axis at a first end and
the pointed region positioned along the axis on a second end,
wherein the axis is straight. The pores can be arranged in rows
such that the larger regions of two pores are in direct contact in
"kissing" arrangement while the smaller regions of the two pores
are spaced apart from one another. A series of pores (such as pores
905a and 905b) are co-axial along a common long axis. One way this
pattern can be achieved is to knit a tubular knit structure with
individual pores wherein at least some of the pores are generally
circular, square or rectangular in shape. The tubular knit can be
stretched longitudinally onto a smaller diameter mandrel to yield
elongated pores which exhibit the kissing or tear drop shaped
pattern; the structure may then be optionally heat set to retain
this shape.
[0073] The above-described, tear drop shaped pore arrangement can
achieve smaller pore sizes using particular wires to form the stent
assembly and pores, such as Nitinol wire in the 0.0005'' to 0.001''
diameter range. The "kissing" pore configuration can achieved
minimum pore widths of 100-250 um and a Length:Width ratio ranging
from 3:1 to 10:1 in an example embodiment.
[0074] While this specification contains many specifics, these
should not be construed as limitations on the scope of an invention
that is claimed or of what may be claimed, but rather as
descriptions of features specific to particular embodiments.
Certain features that are described in this specification in the
context of separate embodiments can also be implemented in
combination in a single embodiment. Conversely, various features
that are described in the context of a single embodiment can also
be implemented in multiple embodiments separately or in any
suitable sub-combination. Moreover, although features may be
described above as acting in certain combinations and even
initially claimed as such, one or more features from a claimed
combination can in some cases be excised from the combination, and
the claimed combination may be directed to a sub-combination or a
variation of a sub-combination. Similarly, while operations are
depicted in the drawings in a particular order, this should not be
understood as requiring that such operations be performed in the
particular order shown or in sequential order, or that all
illustrated operations be performed, to achieve desirable results.
Only a few examples and implementations are disclosed. Variations,
modifications and enhancements to the described examples and
implementations and other implementations may be made based on what
is disclosed.
* * * * *